Liquid control gear



Jan 7l, will., A. N. LAWRENCE' LIQUID CONTROL'- GEAR Filed May 25, 1958INVENTGR ALFRED IV. LAW/Pfwf ATTO R N EY Patented Jan. 7, 1941 PATENTOFFICE p 2,227,593 LIQUID coN'rnoL 'GEAR Alfred N. Lawrence, New York,N. Y., assigner to Sperry Products, Inc., Brooklyn, N. Y., a corporationof New York Application May 25, 1938, Serial No. 209,873

5 Claims.

the type wherein movement of a member at a transmitting station iscaused to control movement of a member at a receiving station. More 5particularly. this invention relates to control gear of this typewherein the transmitting and receiving stations are connected by aliquid transmission system. One such system is shown in the patent to H.S. Hele-Shaw and T. E. Beacham, l No. 1,983,884, granted December 11,1934 in which. the object is to apply a constant torce to the fluidsystem at the transmitting end and to receive a corresponding constantforce at the receiving end. Another such system is shown in lt mycopending application Serial No. 156,630, filed July 31, 1937 (issued as'Patent No. 2,197,554 on April 16, 1940) for Liquid control gear, inwhich the object consists in applying a constantly increasing force atthe transmitting end to over- 2@ come a constantly increasing load attheoperated or receiving end. In eitherof the aforementioned cases, theoperating and operated members will retain any position into which theymay be moved without any tendency on their 25 part to return to acentralized position.

Particularly in the type of transmission system disclosed in mycopending application, a problem arises dueto the fact that the fluid inthe transmission system changes its temperature,

l0 particularly at the receiving end, due to the operation of themechanism at that end, and this causes the parts at the receiving end tobe operated through a predetermined degree over and above the operationwhich has been transmit- 3s ted thereto by the transmitting end. Thus,for instance, in my said copendlng application,` the receiving endoperates a variable pitch propeller mechanism under control of agovernor and it has' been found that temperature variation due .m toheatingup o! the iluid at the receiving end has caused variation inengine speed up -to 200 l R. P. M.

It is the principal object of my invention, therefore, to provide. atransmission system 45 wherein temperature variations will becompensated for in such manner as not to aiect the operation oi themechanism at the receiving end.

Further objects and advantages of this invention will become apparent inthe following de- 50 tail-ed description thereof. In the accompanyingdrawing, l Fig. 1 is an assembly view, with parts sectioned vertically,of a liquid control gear embodying my invention. t .55 Fig. 2 is anenlarged vertical section of a por- (cl. en -54.5)

This invention relates to liquid control gear o! tion of mechanism atthe receiving end, showing a modified arrangement ofthat shown in Wig.1.

I have illustrated my invention as applied to a transmission systemadapted to control the pitch 5 of an aircraft propeller as disclosed inmy said copending application Serial No. 156,630, but it will beunderstood that the invention is capable of broad application whereverthe principle applies.

Referring to the drawing, it will be seen that lo this inventioncomprises three main parts, namely, a transmitting station A, areceiving station B, and a force transferring means, such as aconnecting duct C adapted to be filled with a liquid. It will be,apparent that force applied at l5 one end of the liquid column willcause said coli umn to move through the duct C to operate a member atthe other end of the liquid column. For applying forces to the liquidcolumn for the purpose of transmitting forces, there may be provided acylinder i0 within which operates a trunk' type piston i I. Saidcylinder is connected at one end tothe duct C which is filled withliquid extending up to the said piston. For operating the said piston ina direction to transmit force to the liquid column, there may beprovided `a transmitting element in the form of an operating handle I5pivoted in casing i6 at Il, said lever having a crank arm i8 pivotallyconnected at i9 to the upper end ci a piston rod 20 pivotally 30connected to the piston at 2l. As the handle is moved in the directionof the arrow, the piston is lowered to cause the column of liquid tomove through the duct C. `The force which is applied to the piston isdetermined by a loading spring 22 seated against a bracket 23 xed upon arod 24 pivoted at 25 within the casing i6. The other end of said loadingspring bears against a bracket 26 fixed to a member 2l having a. sleeve28 within which rod 24 may slide, so that said spring is 40 extensible.The member 21 is pivoted at 29 to a crank `arm 30 integral with thecrank arm I 8 and handle I5. The position of the spring and itsconnections is such that the spring acts through a small lever arm toapply a very slight loading force to crank arm I! and the piston Il whenthe piston is in its uppermost position, but

as the handle II is actuated in the direction o! the arrow it will beseen that the spring acts through an increasing lever arm. At the same60 time. however,v the spring is extended so that. while it acts througha larger lever arm it applies a decreasing force as said arm increases.However, the design of the various parts is such that the rate ofdecrease of the compressive force Cil -force which an operator appliesto handle I5 is constant in spite of the increasing force on the piston,and is only suflicient to overcome friction in the system.

The invention is shown applied to a device for controlling a fly ballgovernor which in turn 'controls the pitch of the propeller blades of anairplane propeller in order to enable the airplane engine to operate atits maximum efcient speed.

' Thus, in the example shown in Fig. 1, if it is desired to 'vary thepitch of the propellers, handle |5 is operated in the direction of thearrow, which will cause an element at the receiver end, such as pistonIl', to be moved out of its cylinder and carry therewith a valve stem36. As said valve stem 36 is moved downwardly (in Fig. l) valve '31opens the port38 to connect the same with a source 39 of oil underpressure. 'I'he said port 38 leads to a propeller pitch control deviceto cause the blades of said propeller to be changed in position in adirection to permit the engine to run at higher speed. As the enginespeed picks up in response to the said change in pitch "of thepropeller, the valve stem 36 is caused to be moved upwardly to closeport 38 and retain the propeller blades in the predetermined position.For this purpose, the engine may drive through shaft 40 and suitablegearing 4|, 42 to operate a governor carried by the gear 42, one end 44of each governor element being in engagement with a race 45 around acollar 46 fixed to the valve stem 36. As the speed of the engine picksup, the governor elements will rotate around their pivots 41 to lift thevalve stem against the action of spring 50. Said spring at one endengages a disk 5| fixed to the. valve member 36 and at the other endpresses against the piston Il'. When the speed of the engine has pickedup sufliciently to lift the valve stem 36 so as to close port y38, thenthe pressure which the spring 56 applies to lpiston Il' will be equal tothe force transmitted to the other end of said piston |I' by the pistonII. If the speed of the engine exceeds the desired speed, then the valvestem 36 will be further lifted to uncover port 38 and connect the samewith the return passage 55 to permit some of the oil to drain out andthus shift the propeller blades in the opposite direction to cut downthe speed.v When the engine speed is at the desired point the opposingforce upon one side of said piston l I' will equal the transmitted forceon the other side thereof.

Since in every liquid transmission system of the type described acertain amount of the liquid will leak past the pistons, and since theaccuracy of operation of the system depends upon constancy of volume ofliquid in theitransmission system, means must be provided forperiodically replenishing the fluid in the system to make good any lossor to permit withdrawal of an excess due to temperature expansion, etc.rFor this purpose, applicant has shown the system which is fully shownand described in the said patent to Hele-Shaw No. 1,983,884 and whichconsists of an arm 60 carried by the piston rod 20, designed, each timethe operating lever is moved to its limiting position, to actuate tripmechanism 6| to lift a valve stern 62 to open a valve 63 to permit fluidfroman auxiliary reservoir 64 to communicate with the fluid -in thetransmission system through a passage 65. If there is a deflciency offluid in the transmission system, fluid will be supplied from reservoir64. The valve 63 is normally maintained seated by means of a spring 66.

When there is variation of temperature which may affect `the fluid inthe transmission system, the liquid will tend to expand or contract andcause operation of valve 36 with consequent variation of engine speedabove and below the speed originally set. Thus, in the device shown, theoperation of the governor at end B causes the fluid in the systemadjacent said end to be heated up and has been found to cause variationsin engine speed of as high as 200 R. P. M. The problem thereforeconsists in devising a system whereby the variations in temperature ofthe fluid in the transmission system will not affect the operation ofthe parts controlled at the receiving end. Applicant has solved thisproblem in the following manner: The piston is shown as operating past apacking 'l0 which is similar to a packing past which piston Il operates,and both packings are designed to apply substantially the same amount offrictional resistance to the movement of the respective pistons. Inaddition to packing 10, a second packing |2 is provided for the pistonI' but not for the piston Il, which means that substantially greaterresistance is offered to the movement of piston Il' than to the movementof piston Ii. The consequence of this construction is that if thetransmission fiuid heats up, the tendency of said fluid to operate thepiston Il' to a new operated position and thus affect the operation ofthe pitch controlling mechanism will be counteracted because pistonmoves more easily in response to the pressure in the system than doespiston Il'. Therefore, any adjustment in positionv due to variations intemperature of the transmission fluid will affect the position of pistonbut will not affect the position of piston |I' and hence will introduceno errorin the operation of the operated device at the receiving end.The additional packing 12 may be of s uitahle material such as cork orrubber.

In a modified form of my invention shown in Fig. 2, I have shown adifferent type of packing. In said form the piston is inverted to takethe form of piston H" which operates past an ordinary packing 13 betweenthe piston and the casing 15. The fluid acts upon the upper edge of thepiston which provides an area equal to that of the closed end of pistonIl. As the piston moves past packing 13 which engages the outsidethereof, it also moves past an internal packing 16 which is inengagement with the inner surface thereof Said packing 16 may be held inposition bv reason of the fact that it engages in an annular chamberformed between a fixed cylindrical member 11 depending from cap 18'screwed into the upper end of casing 15, and a flange '|9 at the end ofa stem 80 screw-threaded into the upper end 8| of hollow chamber 82formed within the member 11. The member is provided with a flangeportion 83 which is adapted to engage the upper end of packing 16, whilethe flange 19 engages the lower member. It will now be seen that asflange '|9 is drawn upwardly toward flange 83 by screw threading stem 80upwardly through end 8| of cap 18, the packing 16 will be compressedoutwardly into rm engagement with the iii - understood thatI theapparatus shown is'onlv1 titi dit

iliuotrative and that the invention can be carried ont by otherequivalent means. Also. while it is designed to use the various featuresand elements in the combination and relations described.. borne oi thesemar be altered and others omitted 'vvitinont interferine witb the moregeneral reseits outlined, and tbe invention extends to snob riannedescribed inv invention, vvnat i claim and desire to obtain by LettersPatent is:

in d iiuilanced.remote control system comprisino o transmittins: stationincludine a movable transmitter element, a receiving station including o'nnovable receiver element, a force transferring connection between saidstations whereby movenient oi said transmitter element moves saidreceiver element, means ier applying a load to the transmitter elementindependent of the load eonlied by the operation which is equal to theload Y on the receiver element in every position of said elements, meansopposing tbe movements of said tremitter element, `and means opposingthe movements oi said receiver element, said lastnoined means beingadapted to oi'l'er resistance in encens oi the resistance offered bysaid firstnnined means.

t. d remote control system comprising a transmitting station includingla movable transmitter element. a receiving station including a movablereceiver element, a force transferring connection between said stationswhereby movement of said transmitter element moves said receiverelement, iriotionai means opposino the movements oi said transmitterelement, and irictional means opposino the :movements of said receiverelement, said inet named means beine adaptedto otrerresistance in excessoi the resistance offered by said first named Ineens.

3. A balanced remote control system comprising a transmitting stationincluding a movable transmitter element, a receivine station including amovable receiver element, a duid iorce transferring connection betweensaid stations wherebv 4 movement oi said transmitter element moves saidreceiver element, said connection beine renonsive to temperaturevariationanieans ier aonivine a load to the transmitter elementindependent of the load applied by the operator, which is eduai to theload on the receiver element in eveiv loosition oi said elements, meansonnosino tlie nuovements oi said transmitter eiementI and oneensopposine the movements oi? seid receiver eiernenn seid lest named meansbeine.' eid-rented to oder resistente in encess oi tbe resistance oderedbv seid named menne. n

d., d remote control erstem. comprising o, transmittinti stationinoindino e, movable transmitter element., o receivino stationinclndint; .n movable receiver element, o. duid torce trnnsierrinoconnection between seid stations vvi'ierebv movement oi seidtrnnsinitterelement moves said' receiver element, said connection beineresponsive to teinoernturo variations, irictioned means oonosine themovements oi seid transmitter element, and irictionnl means onnosine themovements oi seid receiver element, said last named means being adaptedto oder resistance in encess oi tbe resistance odered by said niet namedmeans.

5. A remote control system comnvisino n transmittino station including ncvlinder and o. niston movable therein, o receivine station inclndine ncylinder and e. piston movabie tberein, o duid force transferringconnection between seid cvlinders whereby movement ol the piston at thetransmitting station moves said piston et the receiving station, saidconnection beine' responsive to temperature variations, and meansnrodncinn Irictional resistance between eacli piston and its respectivecylinder, the friction production meansdit

